A number of concepts have been proposed that are based on the electron spin, like cellular automata. In particular, spin devices have been suggested, which include a spin transport layer (or STL) above a substrate. Connected to the STL are input and output electrodes. The input electrodes act as spin injection contacts and consist of a magnetic material that is magnetized into one of two possible directions (spin up/down). By passing a current between the input electrodes and the STL, spin-polarized electrons can be accumulated in the STL at the interface between the input electrode and the STL. The spin polarization of electrons at that location in the STL is directly related to the magnetization of the input electrode, i.e. the spins in the STL are also either up or down. The output electrodes convert the local spin polarization at the interface between the STL and the output electrode. Spin polarization is e.g. converted into an electrical signal.
The concepts of input and output electrodes acting as spin injection and spin detection contacts are well described in literature. Also the concept of spin amplification where the magnetization of a detection electrode takes over the spin polarization in a STL is known. In between the input and output electrodes, the spin polarization imprinted by the input electrode propagates by diffusion or drift.
Besides, it has been demonstrated how logic gates can be constructed using majority-logic concepts where several input electrodes polarize the electron spin in the STL and the output electrode detects the average spin polarization that diffuses from those input electrodes to the output electrode.